1. Field of the Invention
The present invention relates to a temperature adjustable seat suitable for a seat in a vehicle, and in particular to a temperature adjustable seat which controls a temperature of a seat by passing a temperature controlled air through an inside thereof.
2. Description of the Related Art
One example of a conventional temperature adjustable seat is disclosed in JP-A-05-277020. The temperature adjustable seat disclosed in JP-A-05-277020 has a structure in which an air heated or cooled by a Peltier device is sent into an inside of the seat by a fan, and then it is spurted from a surface of the seat. Then, an interior space in the car is made comfortable by spurring a cooled air therefrom during a summer, and by spurring a heated air therefrom during a winter.
Further, another example of a conventional temperature adjustable seat is disclosed in JP-A-2002-262962. The temperature adjustable seat disclosed in JP-A-2002-262962 has a structure in which an air heated by a heater is flowed into a cushion of the seat. Then, a temperature inside the vehicle is operated by increasing a flow rate of an air in the seat when the temperature inside the vehicle is higher, or by decreasing a ventilation volume of the seat when the temperature is lower, and also by controlling a flow rate of an air, based on a temperature difference between a surface temperature of the seat and a temperature of the heater.
In the meantime, a person seated on the seat will easily feel a surface temperature and temperature change of the seat because he/she is contacting the seat. As a result, it is desirable that a seat temperature of the temperature adjustable seat is controlled automatically so that the seat temperature reaches to a desired preset temperature and the preset temperature is maintained with high accuracy. In order to automatically control the seat temperature, normally, it is contemplated to simply feedback control a supply current to a Peltier device, heating means, and the like.
However, with such simple feedback control, the responsiveness of the seat surface temperature for a change in the supply current to a Peltier device and the likes is poor. The reasons thereof are that the heat capacity of the seat is large, the first order lag (e.g., a few seconds through a few minutes) is large, and further a wasted time (e.g., a few seconds through a few tens of seconds) required for the air whose temperature is controlled by Peltier device and heating means to reach to a sheet surface is not taken into consideration. As a result, with such simple feedback control, it is difficult to maintain the seat temperature to the preset temperature with high accuracy because the potential for an overshoot is large, and a convergence is poor.
Further, a Peltier device is such that output characteristics per each device a supply current would vary widely. Such variation in output characteristics also becomes a factor of deteriorating thermal control precision.